Found 35 papers in cond-mat
Date of feed: Thu, 12 Oct 2023 00:30:00 GMT

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Manipulating Vortices with Domain Walls in Superconductor-Ferromagnet Heterostructures. (arXiv:2310.06866v1 [cond-mat.supr-con])
Sebastián A. Díaz, Jonas Nothhelfer, Kjetil M. D. Hals, Karin Everschor-Sitte

Vortices are point-like topological defects in superconductors whose motion dictates superconducting properties and controls device performance. In superconductor-ferromagnet heterostructures, vortices interact with topological defects in the ferromagnet such as line-like domain walls. While in previous heterostructure generations, vortex-domain wall interactions were mediated by stray fields; in new heterostructure families, more important become exchange fields and spin-orbit coupling. However, spin-orbit coupling's role in vortex-domain wall interactions remains unexplored. Here we uncover, via numerical simulations and Ginzburg-Landau theory, that Rashba spin-orbit coupling induces magnetoelectric interactions between vortices and domain walls that crucially depend on the wall's winding direction$-$its helicity. The wall's helicity controls whether vortices are pushed or dragged by N\'eel walls, and their gliding direction along Bloch walls. Our work capitalizes on interactions between topological defects from different order parameters and of different dimensionality to engineer enhanced functionality.

Dynamics of vacancy-induced modes in the non-Abelian Kitaev spin liquid. (arXiv:2310.06891v1 [cond-mat.str-el])
Wen-Han Kao, Gábor B. Halász, Natalia B. Perkins

We study the dynamical response of vacancy-induced quasiparticle excitations in the site-diluted Kitaev spin liquid with a magnetic field. Due to the flux-binding effect and the emergence of dangling Majorana fermions around each spin vacancy, the low-energy physics is governed by a set of vacancy-induced quasi-zero-energy modes. These localized modes result in unique characteristics of the dynamical spin correlation functions, which intriguingly mimic the single-quasiparticle density of states and further exhibit a quasi-zero-frequency peak. By recognizing the potential observability of these local correlation functions via scanning tunneling microscopy (STM), we show how the STM response is sensitive to the local flux configuration, the magnetic field strength, and the vacancy concentration. Constructing a simple model of the localized modes, we also elucidate how the local correlation functions can be interpreted in terms of the hybridization between these modes.

Fault-tolerant logical gates via constant depth circuits and emergent symmetries on non-orientable topological stabilizer and Floquet codes. (arXiv:2310.06917v1 [quant-ph])
Ryohei Kobayashi, Guanyu Zhu

We consider the topological stabilizer code and Floquet code defined on a non-orientable surface, which can be considered as families of codes extending Shor's 9-qubit code. We investigate the fault-tolerant logical gates of the $\mathbb{Z}_2$ toric code in this setup, which corresponds to $e\leftrightarrow m$ exchanging symmetry of the underlying $\mathbb{Z}_2$ gauge theory. We find that non-orientable geometry provides a new way the emergent symmetry acts on the code space, and discover the new realization of the fault-tolerant Hadamard gate of 2d $\mathbb{Z}_2$ toric code on a surface with a single cross-cap, dubbed an $\mathbb{RP}^2$ code. This Hadamard gate can be realized by a constant-depth local unitary circuit modulo non-locality caused by a cross-cap, thus reduces the error propagation and eliminates the problem of the factor-of-two distance reduction compared with the previously known realization on a surface code. Via folding, the $\mathbb{RP}^2$ code can be turned into a bilayer local quantum code, where the folded cross-cap is equivalent to a bi-layer twist terminated on a gapped boundary and the logical Hadamard only contains local gates with intra-layer couplings. We further obtain the complete logical Clifford gate set for a stack of $\mathbb{RP}^2$ codes. We then construct the honeycomb Floquet code in the presence of a single cross-cap, and find that the period of the sequential Pauli measurements acts as a $HZ$ logical gate on the single logical qubit, where the cross-cap enriches the dynamics compared with the orientable case. We find that the dynamics of the honeycomb Floquet code is precisely described by a condensation operator of the $\mathbb{Z}_2$ gauge theory, and illustrate the exotic dynamics of our code in terms of a condensation operator supported at a non-orientable surface.

In-plane magnetic field-driven conductance modulations in topological insulator kinks. (arXiv:2310.06924v1 [cond-mat.mes-hall])
Gerrit Behner, Kristof Moors, Yong Zhang, Michael Schleenvoigt, Alina Rupp, Erik Zimmermann, Abdur Rehman Jalil, Peter Schüffelgen, Hans Lüth, Detlev Grützmacher, Thomas Schäpers

We present low-temperature magnetoconductance measurements on Bi$_{1.5}$Sb$_{0.5}$Te$_{1.8}$Se$_{1.2}$ kinks with ribbon-shaped legs. The conductance displays a clear dependence on the in-plane magnetic field orientation. The conductance modulation is consistent with orbital effect-driven trapping of the topological surface states on different side facets of the legs of the kink, which affects their transmission across the kink. This magnetic field-driven trapping and conductance pattern can be explained with a semiclassical picture and is supported by quantum transport simulations. The interpretation is corroborated by varying the angle of the kink and analyzing the temperature dependence of the observed magnetoconductance pattern, indicating the importance of phase coherence along the cross section perimeter of the kink legs.

Modulating Resonant Electronic Coupling of Tungsten Diselenide Monolayers with Vanadyl Phthalocyanine for Spin-Valley Polarization Control. (arXiv:2310.06979v1 [cond-mat.mes-hall])
Daphné Lubert-Perquel, Jeffrey L. Blackburn, Byeong Wook Cho, Young Hee Lee, Justin C. Johnson

Combining the synthetic tunability of molecular compounds with the optical selection rules of transition metal dichalcogenides (TMDC) that derive from spin-valley coupling could provide interesting opportunities for the readout of quantum information. However, little is known about the electronic and spin interactions at such interfaces and the influence on spin-valley relaxation. In this work we investigate various heterojunctions of vanadyl phthalocyanine (VOPc) thermally evaporated on WSe$_2$ and find that local ordering of the molecular layer plays an important role in the electronic perturbation of WSe$_2$, which in turn directly influences the spin-valley polarization lifetime. A thin molecular layer results in a hybrid state which destroys the spin-valley polarization almost instantaneously, whereas a thicker molecular layer with well-defined local ordering shows minimal electronic perturbation and results in longer-lived spin-valley polarization than the WSe$_2$ monolayer alone.

Universal and nonuniversal probability laws in Markovian open quantum dynamics subject to generalized reset processes. (arXiv:2310.06981v1 [cond-mat.stat-mech])
Federico Carollo, Igor Lesanovsky, Juan P. Garrahan

We consider quantum jump trajectories of Markovian open quantum systems subject to stochastic in time resets of their state to an initial configuration. The reset events provide a partitioning of quantum trajectories into consecutive time intervals, defining sequences of random variables from the values of a trajectory observable within each of the intervals. For observables related to functions of the quantum state, we show that the probability of certain orderings in the sequences obeys a universal law. This law does not depend on the chosen observable and, in case of Poissonian reset processes, not even on the details of the dynamics. When considering (discrete) observables associated with the counting of quantum jumps, the probabilities in general lose their universal character. Universality is only recovered in cases when the probability of observing equal outcomes in a same sequence is vanishingly small, which we can achieve in a weak reset rate limit. Our results extend previous findings on classical stochastic processes [N.~R.~Smith et al., EPL {\bf 142}, 51002 (2023)] to the quantum domain and to state-dependent reset processes, shedding light on relevant aspects for the emergence of universal probability laws.

Many-body Chern insulator in the Kondo lattice model on a triangular lattice. (arXiv:2310.07094v1 [cond-mat.str-el])
Kota Ido, Takahiro Misawa

The realization of topological insulators induced by correlation effects is one of the main issues of modern condensed matter physics. An intriguing example of the correlated topological insulators is a magnetic Chern insulator induced by a noncoplanar multiple-Q magnetic order. Although the realization of the magnetic Chern insulator has been studied in the classical limit of the Kondo lattice model, research on the magnetic Chern insulator in the original Kondo lattice model is limited. Here, we investigate the possibility of the many-body Chern insulator with the noncoplanar triple-Q magnetic order in the Kondo lattice model on a triangular lattice. Using the many-variable variational Monte Carlo method, we reveal that the triple-Q magnetic order becomes a ground state at quarter filling in an intermediate Kondo coupling region. We also show that the many-body Chern number is quantized to one in the triple-Q magnetic ordered phase utilizing the polarization operators. Our results provide a pathway for the realization of the many-body Chern insulator in correlated electron systems.

Absence of topological Hall effect in Fe$_x$Rh$_{100-x}$ epitaxial films: revisiting their phase diagram. (arXiv:2310.07140v1 [cond-mat.mtrl-sci])
Xiaoyan Zhu, Hui Li, Jing Meng, Xinwei Feng, Zhixuan Zhen, Haoyu Lin, Bocheng Yu, Wenjuan Cheng, Dongmei Jiang, Yang Xu, Tian Shang, Qingfeng Zhan

A series of Fe$_x$Rh$_{100-x}$ ($30 \leq x \leq 57$) films were epitaxially grown using magnetron sputtering, and were systematically studied by magnetization-, electrical resistivity-, and Hall resistivity measurements. After optimizing the growth conditions, phase-pure Fe$_{x}$Rh$_{100-x}$ films were obtained, and their magnetic phase diagram was revisited. The ferromagnetic (FM) to antiferromagnetic (AFM) transition is limited at narrow Fe-contents with $48 \leq x \leq 54$ in the bulk Fe$_x$Rh$_{100-x}$ alloys. By contrast, the FM-AFM transition in the Fe$_x$Rh$_{100-x}$ films is extended to cover a much wider $x$ range between 33 % and 53 %, whose critical temperature slightly decreases as increasing the Fe-content. The resistivity jump and magnetization drop at the FM-AFM transition are much more significant in the Fe$_x$Rh$_{100-x}$ films with $\sim$50 % Fe-content than in the Fe-deficient films, the latter have a large amount of paramagnetic phase. The magnetoresistivity (MR) is rather weak and positive in the AFM state, while it becomes negative when the FM phase shows up, and a giant MR appears in the mixed FM- and AFM states. The Hall resistivity is dominated by the ordinary Hall effect in the AFM state, while in the mixed state or high-temperature FM state, the anomalous Hall effect takes over. The absence of topological Hall resistivity in Fe$_{x}$Rh$_{100-x}$ films with various Fe-contents implies that the previously observed topological Hall effect is most likely extrinsic. We propose that the anomalous Hall effect caused by the FM iron moments at the interfaces nicely explains the hump-like anomaly in the Hall resistivity. Our systematic investigations may offer valuable insights into the spintronics based on iron-rhodium alloys.

Temperature-Dependent Collective Excitations in a Three-Dimensional Dirac System ZrTe$_{5}$. (arXiv:2310.07232v1 [cond-mat.str-el])
Zijian Lin, Cuixiang Wang, Daqiang Chen, Sheng Meng, Youguo Shi, Jiandong Guo, Xuetao Zhu

Zirconium pentatelluride (ZrTe$_{5}$), a system with a Dirac linear band across the Fermi level and anomalous transport features, has attracted considerable research interest for it is predicted to be located at the boundary between strong and weak topological insulators separated by a topological semimetal phase. However, the experimental verification of the topological phase transition and the topological ground state in ZrTe$_{5}$ is full of controversies, mostly due to the difficulty of precisely capturing the small gap evolution with single-particle band structure measurements. Alternatively, the collective excitations of electric charges, known as plasmons, in Dirac systems exhibiting unique behavior, can well reflect the topological nature of the band structure. Here, using reflective high-resolution electron energy loss spectroscopy (HREELS), we investigate the temperature-dependent collective excitations of ZrTe$_{5}$, and discover that the plasmon energy in ZrTe$_{5}$ is proportional to the $1/3$ power of the carrier density $n$, which is a unique feature of plasmons in three-dimensional Dirac systems \lyxadded{51189}{Wed Sep 13 06:29:07 2023}{or hyperbolic topological insulators}. Based on this conclusion, the origin of the resistivity anomaly of ZrTe$_{5}$ can be attributed to the temperature-dependent chemical potential shift in extrinsic Dirac semimetals.

Ultimate sharpness of the tunneling resonance in vertical heterostructures. (arXiv:2310.07307v1 [cond-mat.mes-hall])
Georgy Alymov, Dmitry Svintsov

Heterostructures comprised of two two-dimensional electron systems (2DES) separated by a dielectric exhibit resonant tunneling when the band structures of both systems are aligned. It is commonly assumed that the height and width of the resonant peak in the tunneling current is determined by electron scattering and rotational misalignment of crystal structures of the 2DES. We identify two fundamental factors limiting the maximum height and steepness of the resonance: coupling to contacts and tunnel splitting of energy levels. The upper limit of the tunneling current is the number of electrons available for tunneling times half the tunnel coupling between the 2DES. As a result of a tradeoff between the contact-induced level broadening and contact resistance, the maximum current is only achievable when the coupling to contacts equals the tunnel level splitting. According to our model calculations, the limiting behavior can be observed in double-gated graphene/few-layer hexagonal boron nitride/graphene heterostructures.

Frequency mixing spectroscopy of spins in diamond. (arXiv:2310.07398v1 [quant-ph])
Mohammed Attrash, Sergei Masis, Sergey Hazanov, Oleg Shtempluck, Eyal Buks

Frequency mixing processes in spin systems have a variety of applications in meteorology and in quantum data processing. Spin spectroscopy based on frequency mixing offers some advantages, including the ability to eliminate crosstalk between driving and detection. We experimentally explore nonlinear frequency mixing processes with negatively charged nitrogen-vacancy defects in diamond at low temperatures, and near level anti crossing. The experimental setup allows simultaneously applying magnetic driving in the longitudinal and transverse directions. Magnetic resonance detection is demonstrated using both Landau Zener St\"uckelberg interferometry and two-tone driving spectroscopy. The experimental results are compared with predictions of a theoretical analysis based on the rotating wave approximation.

Superfluidity meets the solid-state: frictionless mass-transport through a (5,5) carbon-nanotube. (arXiv:2310.07476v1 [cond-mat.mtrl-sci])
Alberto Ambrosetti, Pier Luigi Silvestrelli, Luca Salasnich

Superfluidity is a well-characterized quantum phenomenon which entails frictionless-motion of mesoscopic particles through a superfluid, such as $^4$He or dilute atomic-gases at very low temperatures. As shown by Landau, the incompatibility between energy- and momentum-conservation, which ultimately stems from the spectrum of the elementary excitations of the superfluid, forbids quantum-scattering between the superfluid and the moving mesoscopic particle, below a critical speed-threshold. Here we predict that frictionless-motion can also occur in the absence of a standard superfluid, i.e. when a He atom travels through a narrow (5,5) carbon-nanotube (CNT). Due to the quasi-linear dispersion of the plasmon and phonon modes that could interact with He, the (5,5) CNT embodies a solid-state analog of the superfluid, thereby enabling straightforward transfer of Landau's criterion of superfluidity. As a result, Landau's equations acquire broader generality, and may be applicable to other nanoscale friction phenomena, whose description has been so far purely classical.

Terahertz s-SNOM reveals nanoscale conductivity of graphene. (arXiv:2310.07479v1 [physics.optics])
Henrik B. Lassen, Edmund J. R. Kelleher, Leonid Iliushyn, Timothy J. Booth, Peter Bøggild, Peter U. Jepsen

The nanoscale contrast in scattering-type scanning near-field optical microscopy (s-SNOM) is determined by the optical properties of the sample immediately under the apex of the tip of the atomic force microscope (AFM). There are several models that describe the optical scattering of an incident field by the tip near a surface, and these models have been successful in relating the measured scattering signal to the dielectric function of the sample under the tip. Here, we address a situation that is normally not considered in the existing interaction models, namely the near-field signal arising from thin, highly conductive films in the terahertz (THz) frequency range. According to established theoretical models, highly conductive thin films should show insignificant contrast in the THz range for small variations in conductivity, therefore hindering the use of s-SNOM for nanoscale characterisation. We experimentally demonstrate unexpected but clear and quantifiable layer contrast in the THz s-SNOM signal from few-layer exfoliated graphene as well as subtle nanoscale contrast variations within graphene layers. We use finite-element simulations to confirm that the observed contrast is described by the classical electromagnetics of the scattering mechanism, suggesting that the dipole models must be reformulated to correctly describe the interaction with conductive samples.

Iterative solution of relativistic Boltzmann equation in curved spacetime with application to kinetic coefficients. (arXiv:2310.07481v1 [gr-qc])
Long Cui, Xin Hao, Liu Zhao

Under relaxation time approximation, we obtain an iterative solution to the relativistic Boltzmann equation in generic stationary spacetime. This solution provides a scheme to study non-equilibrium system order by order. As a specific example, we analytically calculated the covariant expressions of the particle flow and the energy momentum tensor up to the first order in relaxation time. Finally and most importantly, we present all 14 kinetic coefficients for a neutral system, which are verified to satisfy the Onsager reciprocal relation and guarantee a non-negative entropy production.

Electronic States in Helical Materials: General Properties and Application to InSeI. (arXiv:2310.07530v1 [cond-mat.mtrl-sci])
Jiaming Hu, Shu Zhao, Wenbin Li, Hua Wang

In this article, we systematically explore several key properties of electronic states in helical materials systems, including the inheritance of orbital angular momentum (OAM) from local atomic orbitals to the entire helical structure, the conservation of helical momentum, and the emergence of helical-induced spin-orbit coupling (hSOC). We then apply this comprehensive theoretical framework to elucidate the electronic structure of one-dimensional (1D) helical crystal InSeI. Our analysis reveals the influence of hSOC, evident in spin-mixing energy gaps within the electronic band structure, as calculated through density functional theory. Utilizing a combination of tight-binding modeling and first-principles calculations, we ascertain the spin-polarized electric response and the chiral-switchable second-order photocurrent response of InSeI, characterized as the Landauer-Buttiker ballistic transport and shift current response. The results highlight the potential of 1D InSeI for applications in spintronics and optoelectronics. The overarching theoretical framework established in this work will prove invaluable for the investigation of other helical electronic systems.

Anomalous quasiparticle lifetime in geometric quantum critical metals. (arXiv:2310.07539v1 [cond-mat.str-el])
Hao Song, Han Ma, Catherine Kallin, Sung-Sik Lee

Metals can undergo geometric quantum phase transitions where the local curvature of the Fermi surface changes sign without a change in symmetry or topology. At the inflection points on the Fermi surface, the local curvature vanishes, leading to an anomalous dynamics of quasiparticles. In this paper, we study geometric quantum critical metals that support inflection points in two dimensions, and show that the decay rate of quasiparticles goes as $E^{\alpha}$ with $1<\alpha<2$ as a function of quasiparticle energy $E$ at the inflection points.

Latent Su-Schrieffer-Heeger models. (arXiv:2310.07619v1 [cond-mat.mes-hall])
Malte Röntgen, Xuelong Chen, Wenlong Gao, Maxim Pyzh, Peter Schmelcher, Vincent Pagneux, Vassos Achilleos, Antonin Coutant

The Su-Schrieffer-Heeger (SSH) chain is the reference model of a one-dimensional topological insulator. Its topological nature can be explained by the quantization of the Zak phase, due to reflection symmetry of the unit cell, or of the winding number, due to chiral symmetry. Here, we harness recent graph-theoretical results to construct families of setups whose unit cell features neither of these symmetries, but instead a so-called latent or hidden reflection symmetry. This causes the isospectral reduction -- akin to an effective Hamiltonian -- of the resulting lattice to have the form of an SSH model. As we show, these latent SSH models exhibit features such as multiple topological transitions and edge states, as well as a quantized Zak phase. Relying on a generally applicable discrete framework, we experimentally validate our findings using electric circuits.

Fountains of Flat Bands through Moir\'e Engineering. (arXiv:2310.07647v1 [cond-mat.mes-hall])
Xiaoting Zhou, Yi-Chun Hung, Baokai Wang, Arun Bansil

Moir\'e Engineering offers an exceptional foundation for creating controllable systems that display strongly correlated physics. The central focus is on isolated flat bands near the Fermi level, stemming from the pseudo-Landau levels of the massless or massive Dirac fermions. Unlike spin-1/2 fermions, both the Lieb and Dice lattices host triply degenerate spin-1 fermions as the low-energy effective quasi-particles. In this letter, we propose Moir\'e structures, respectively, of the twisted bilayer Lieb and Dice lattices, which exhibit tunable numbers of isolated flat bands near the Fermi level. The quantity of isolated flat bands directly relates to the size of the Moir\'e supercell, for they originate from the flat bands of the bipartite Lieb or Dice lattice. These flat bands remain isolated from the high-energy bands even with small higher-order term and chiral-symmetry breaking interlayer tunneling considered. At a small twist angle, thousands of isolated flat bands can be generated by the Moir\'e pattern, which significantly amplifies the flat band physics. The dramatic change in the number of flat bands in the Moir\'e Brillouin zone as the twist angle varies gives rise to a new platform to effectively manipulate the strongly correlated physics. Moreover, via the investigation of the systems, we have demonstrated that these isolated flat bands exhibit considerable quantum weight, indicating a notable superfluid weight upon adding BCS-type pairing potential. Further, the density-of-state around the Fermi level as a function of the twisted angle contributed by these flat bands implies a tunable critical temperature for BCS superconductivity. Most importantly, through twisted bilayer Lieb lattice and twisted Dice lattice, we demonstrate that the Moir\'e engineering of bipartite lattices creates a brand new path toward the engineering of the flat-band generation.

Semiclassical quantization conditions in strained moir\'e lattices. (arXiv:2206.03349v3 [math.AP] UPDATED)
Simon Becker, Jens Wittsten

In this article we generalize the Bohr-Sommerfeld rule for scalar symbols at a potential well to matrix-valued symbols having eigenvalues that may coalesce precisely at the bottom of the well. As an application, we study the existence of approximately flat bands in moir\'e heterostructures such as strained two-dimensional honeycomb lattices in a model recently introduced by Timmel and Mele.

Fast quantum transfer mediated by topological domain walls. (arXiv:2208.00797v5 [quant-ph] UPDATED)
Juan Zurita, Charles E. Creffield, Gloria Platero

The duration of bidirectional transfer protocols in 1D topological models usually scales exponentially with distance. In this work, we propose transfer protocols in multidomain SSH chains and Creutz ladders that lose the exponential dependence, greatly speeding up the process with respect to their single-domain counterparts, reducing the accumulation of errors and drastically increasing their performance, even in the presence of symmetry-breaking disorder. We also investigate how to harness the localization properties of the Creutz ladder-with two localized modes per domain wall-to choose the two states along the ladder that will be swapped during the transfer protocol, without disturbing the states located in the intermediate walls between them. This provides a 1D network with all-to-all connectivity that can be helpful for quantum information purposes.

Pauli topological subsystem codes from Abelian anyon theories. (arXiv:2211.03798v2 [quant-ph] UPDATED)
Tyler D. Ellison, Yu-An Chen, Arpit Dua, Wilbur Shirley, Nathanan Tantivasadakarn, Dominic J. Williamson

We construct Pauli topological subsystem codes characterized by arbitrary two-dimensional Abelian anyon theories--this includes anyon theories with degenerate braiding relations and those without a gapped boundary to the vacuum. Our work both extends the classification of two-dimensional Pauli topological subsystem codes to systems of composite-dimensional qudits and establishes that the classification is at least as rich as that of Abelian anyon theories. We exemplify the construction with topological subsystem codes defined on four-dimensional qudits based on the $\mathbb{Z}_4^{(1)}$ anyon theory with degenerate braiding relations and the chiral semion theory--both of which cannot be captured by topological stabilizer codes. The construction proceeds by "gauging out" certain anyon types of a topological stabilizer code. This amounts to defining a gauge group generated by the stabilizer group of the topological stabilizer code and a set of anyonic string operators for the anyon types that are gauged out. The resulting topological subsystem code is characterized by an anyon theory containing a proper subset of the anyons of the topological stabilizer code. We thereby show that every Abelian anyon theory is a subtheory of a stack of toric codes and a certain family of twisted quantum doubles that generalize the double semion anyon theory. We further prove a number of general statements about the logical operators of translation invariant topological subsystem codes and define their associated anyon theories in terms of higher-form symmetries.

Geometric phases of mixed quantum states: A comparative study of interferometric and Uhlmann phases. (arXiv:2301.01210v3 [quant-ph] UPDATED)
Xu-Yang Hou, Xin Wang, Zheng Zhou, Hao Guo, Chih-Chun Chien

Two geometric phases of mixed quantum states, known as the interferometric phase and Uhlmann phase, are generalizations of the Berry phase of pure states. After reviewing the two geometric phases and examining their parallel-transport conditions, we specify a class of cyclic processes that are compatible with both conditions and therefore accumulate both phases through their definitions, respectively. Those processes then facilitate a fair comparison between the two phases. We present exact solutions of two-level and three-level systems to contrast the two phases. While the interferometric phase exhibits finite-temperature transitions only in the three-level system but not the two-level system, the Uhlmann phase shows finite-temperature transitions in both cases. Thus, using the two geometric phases as finite-temperature topological indicators demonstrates the rich physics of topology of mixed states.

General mapping of one-dimensional non-Hermitian mosaic models to non-mosaic counterparts: Mobility edges and Lyapunov exponents. (arXiv:2301.01711v3 [cond-mat.dis-nn] UPDATED)
Sheng-Lian Jiang, Yanxia Liu, Li-Jun Lang

We establish a general mapping from one-dimensional non-Hermitian mosaic models to their non-mosaic counterparts. This mapping can give rise to mobility edges and even Lyapunov exponents in the mosaic models if critical points of localization or Lyapunov exponents of localized states in the corresponding non-mosaic models have already been analytically solved. To demonstrate the validity of this mapping, we apply it to two non-Hermitian localization models: an Aubry-Andr\'e-like model with nonreciprocal hopping and complex quasiperiodic potentials, and the Ganeshan-Pixley-Das Sarma model with nonreciprocal hopping. We successfully obtain the mobility edges and Lyapunov exponents in their mosaic models. This general mapping may catalyze further studies on mobility edges, Lyapunov exponents, and other significant quantities pertaining to localization in non-Hermitian mosaic models.

EuCd$_2$As$_2$: a magnetic semiconductor. (arXiv:2301.08014v2 [cond-mat.mtrl-sci] UPDATED)
D. Santos-Cottin, I. Mohelský, J. Wyzula, F. Le Mardelé, I. Kapon, S. Nasrallah, N. BarišIć, I. Živković, J. R. Soh, F. Guo, K. Rigaux, M. Puppin, J. H. Dil, B. Gudac, Z. Rukelj, M. Novak, A. B. Kuzmenko, C. C. Homes, Tomasz Dietl, M. Orlita, Ana Akrap

EuCd$_2$As$_2$ is now widely accepted as a topological semimetal in which a Weyl phase is induced by an external magnetic field. We challenge this view through firm experimental evidence using a combination of electronic transport, optical spectroscopy and excited-state photoemission spectroscopy. We show that the EuCd$_2$As$_2$ is in fact a semiconductor with a gap of 0.77 eV. We show that the externally applied magnetic field has a profound impact on the electronic band structure of this system. This is manifested by a huge decrease of the observed band gap, as large as 125~meV at 2~T, and consequently, by a giant redshift of the interband absorption edge. However, the semiconductor nature of the material remains preserved. EuCd$_2$As$_2$ is therefore a magnetic semiconductor rather than a Dirac or Weyl semimetal, as suggested by {\em ab initio} computations carried out within the local spin-density approximation.

Design of linear block copolymers and ABC star terpolymers that produce two length scales at phase separation. (arXiv:2304.14194v2 [cond-mat.soft] UPDATED)
Merin Joseph, Daniel J. Read, Alastair M. Rucklidge

Quasicrystals (materials with long range order but without the usual spatial periodicity of crystals) were discovered in several soft matter systems in the last twenty years. The stability of quasicrystals has been attributed to the presence of two prominent length scales in a specific ratio, which is 1.93 for the twelve-fold quasicrystals most commonly found in soft matter. We propose design criteria for block copolymers such that quasicrystal-friendly length scales emerge at the point of phase separation from a melt, basing our calculations on the Random Phase Approximation. We consider two block copolymer families: linear chains containing two different monomer types in blocks of different lengths, and ABC star terpolymers. In all examples, we are able to identify parameter windows with the two length scales having a ratio of 1.93. The models that we consider that are simplest for polymer synthesis are, first, a monodisperse A_L B A_S B melt and, second, a model based on random reactions from a mixture of A_L, A_S and B chains: both feature the length scale ratio of 1.93 and should be relatively easy to synthesise.

A Chern-Simons theory for dipole symmetry. (arXiv:2305.02492v3 [cond-mat.str-el] UPDATED)
Xiaoyang Huang

We present effective field theories for dipole symmetric topological matters that can be described by the Chern-Simons theory. Unlike most studies using higher-rank gauge theory, we develop a framework with both U(1) and dipole gauge fields. As a result, only the highest multipole symmetry can support the 't Hooft anomaly. We show that with appropriate point group symmetries, the dipolar Chern-Simons theory can exist in any dimension and, moreover, the bulk-edge correspondence can depend on the boundary. As two applications, we draw an analogy between the dipole anomaly and the torsional anomaly and generalize particle-vortex duality to dipole phase transitions. All of the above are in the flat spacetime limit, but our framework is able to systematically couple dipole symmetry to curved spacetime. Based on that, we give a proposal about anomalous dipole hydrodynamics. Moreover, we show that the fracton-elasticity duality arises naturally from a non-abelian Chern-Simons theory in 3D.

On the Topological Protection of the Quantum Hall Effect in a Cavity. (arXiv:2305.10558v2 [cond-mat.mes-hall] UPDATED)
Vasil Rokaj, Jie Wang, John Sous, Markus Penz, Michael Ruggenthaler, Angel Rubio

We study the quantum Hall effect in a two-dimensional homogeneous electron gas coupled to a quantum cavity field. As initially pointed out by Kohn, Galilean invariance for a homogeneous quantum Hall system implies that the electronic center of mass (CM) decouples from the electron-electron interaction, and the energy of the CM mode, also known as Kohn mode, is equal to the single particle cyclotron transition. In this work, we point out that strong light-matter hybridization between the Kohn mode and the cavity photons gives rise to collective hybrid modes between the Landau levels and the photons. We provide the exact solution for the collective Landau polaritons and we demonstrate the weakening of topological protection at zero temperature due to the existence of the lower polariton mode which is softer than the Kohn mode. This provides an intrinsic mechanism for the recently observed topological breakdown of the quantum Hall effect in a cavity [Appugliese et al., Science 375, 1030-1034 (2022)]. Importantly, our theory predicts the cavity suppression of the thermal activation gap in the quantum Hall transport. Our work paves the way for future developments in the cavity control of quantum materials.

Coexistence of extended and localized states in finite-sized mosaic Wannier-Stark lattices. (arXiv:2306.10831v2 [cond-mat.dis-nn] UPDATED)
Jun Gao, Ivan M. Khaymovich, Adrian Iovan, Xiao-Wei Wang, Govind Krishna, Ze-Sheng Xu, Emrah Tortumlu, Alexander V. Balatsky, Val Zwiller, Ali W. Elshaari

Quantum transport and localization are fundamental concepts in condensed matter physics. It is commonly believed that in one-dimensional systems, the existence of mobility edges is highly dependent on disorder. Recently, there has been a debate over the existence of an exact mobility edge in a modulated mosaic model without quenched disorder, the so-called mosaic Wannier-Stark lattice. Here, we experimentally implement such disorder-free mosaic photonic lattices using a silicon photonics platform. By creating a synthetic electric field, we could observe energy-dependent coexistence of both extended and localized states in a finite number of waveguides. The Wannier-Stark ladder emerges when the resulting potential is strong enough, and can be directly probed by exciting different spatial modes of the lattice. Our studies provide the experimental proof of coexisting sets of strongly localized and conducting (though weakly localized) states in finite-sized mosaic Wannier-Stark lattices, which hold the potential to encode high-dimensional quantum resources with compact and robust structures.

Selective Manipulation and Tunneling Spectroscopy of Broken-Symmetry Quantum Hall States in a Hybrid-edge Quantum Point Contact. (arXiv:2307.15728v2 [cond-mat.mes-hall] UPDATED)
Wei Ren, Xi Zhang, Jaden Ma, Xihe Han, Kenji Watanabe, Takashi Taniguchi, Ke Wang

We present a device architecture of hybrid-edge and dual-gated quantum point contact. We demonstrate improved electrostatic control over the separation, position, and coupling of each broken-symmetry compressible strip in graphene. Via low-temperature magneto-transport measurement, we demonstrate selective manipulation over the evolution, hybridization, and transmission of arbitrarily chosen quantum Hall states in the channel. With gate-tunable tunneling spectroscopy, we characterize the energy gap of each symmetry-broken quantum Hall state with high resolution on the order of ~0.1 meV.

Accelerating micromagnetic and atomistic simulations using multiple GPUs. (arXiv:2308.08447v2 [cond-mat.mes-hall] UPDATED)
Serban Lepadatu

It is shown micromagnetic and atomistic spin dynamics simulations can use multiple GPUs in order to reduce computation time, but also to allow for a larger simulation size than is possible on a single GPU. Whilst interactions which depend on neighbouring spins, such as exchange interactions, may be implemented efficiently by transferring data between GPUs using halo regions, or alternatively using direct memory accesses, implementing the long-range demagnetizing interaction is the main difficulty in achieving good performance scaling, where the data transfer rate between GPUs is a significant bottleneck. A multi-GPU convolution algorithm is developed here, which relies on single-GPU FFTs executed in parallel. It is shown that even for micromagnetic simulations where the demagnetizing interaction computation time dominates, good performance scaling may be achieved, with speedup factors up to 1.8, 2.5, and 3.1, for 2, 3, and 4 GPUs respectively. The code developed here can be used for any number of GPUs in parallel, with performance scaling strongly dependent on inter-GPU data transfer rate and connection topology. This is further improved in micromagnetic simulations which include a spin transport solver, obtaining speedup factors up to 1.96, 2.8, and 3.7, for 2, 3, and 4 GPUs respectively. The best case scenario is obtained for atomistic spin dynamics simulations, where the demagnetizing interaction is implemented with spin-averaged cells. Using a single workstation with 4 GPUs, it is shown atomistic spin dynamics simulations with up to 1 billion spins, and atomistic Monte Carlo simulations with up to 2 billion spins are possible, with a near-ideal performance scaling.

Predicting Psi-BN: computational insights into its mechanical, electronic, and optical characteristics. (arXiv:2308.13112v2 [cond-mat.mtrl-sci] UPDATED)
F. F. Monteiro, K. A. L. Lima, L. A. Ribeiro Junior

Computational materials are pivotal in advancing our understanding of distinct material classes and their properties, offering valuable insights in predicting novel structures and complementing experimental approaches. In this context, Psi-graphene is a stable two-dimensional carbon allotrope composed of 5-6-7 carbon rings theoretically predicted recently. Using density functional theory (DFT) calculations, we explored its boron nitride counterpart's mechanical, electronic, and optical characteristics (Psi-BN). Our results indicate that Psi-BN possesses a band gap of 4.59 eV at the HSE06 level. Phonon calculations and ab initio molecular dynamics simulations demonstrated that this material has excellent structural and dynamic stability. Moreover, its formation energy is -7.48 eV. Psi-BN exhibited strong ultraviolet activity, suggesting its potential as an efficient UV collector. Furthermore, we determined critical mechanical properties of Psi-BN, such as the elastic stiffness constants, Young's modulus (250-300 GPa), and Poisson ratio (0.7), providing valuable insights into its mechanical behavior.

Dislocation breakaway from nanoparticle array linear complexions: Plasticity mechanisms and strength scaling laws. (arXiv:2308.15744v2 [cond-mat.mtrl-sci] UPDATED)
Divya Singh, Daniel S. Gianola, Timothy J. Rupert

Linear complexions are stable defect states, where the stress field associated with a dislocation induces a local phase transformation that remains restricted to nanoscale dimensions. As these complexions are born at the defects which control plasticity in metals, it is crucial to understand their impact on subsequent mechanical properties. In this work, atomistic modeling is used to understand how dislocation mechanics are altered by the presence of nanoparticle array linear complexions in a Ni-Al alloy. Molecular dynamics simulations are used to identify the critical shear stress needed to drive dislocation breakaway, first for nanoparticle arrays formed by Monte Carlo/molecular dynamics methods to represent realistic configurations and subsequently for simplified models that allow the effects of particle spacing and size to be varied in a controlled manner. A combined bowing and progressive unpinning mechanism is uncovered, leading to the demonstration of a new strength scaling law that differs in keys ways from classical Orowan bowing.

Strong relevance of Zinc impurity in the spin-$\frac{1}{2}$ Kagome quantum antiferromagnets: a variational study. (arXiv:2309.04363v2 [cond-mat.str-el] UPDATED)
Jianhua Yang, Tao Li

Copper hydroxyhalide materials herbertsmithite ZnCu$_{3}$(OH)$_{6}$Cl$_{2}$ and Zn-barlowite ZnCu$_{3}$(OH)$_{6}$FrBr are thought to be the best realizations of the spin-$\frac{1}{2}$ Kagome quantum antiferromagnetic Heisenberg model and are widely believed to host a spin liquid ground state. However, the exact nature of such a novel state of matter is still under strong debate, partly due to the complication related to the occupation disorder between the Zinc and the Copper ions in these systems. In particular, recent nuclear magnetic resonance measurements indicate that the magnetic response of the Kagome plane is significantly spatial inhomogeneous, even though the content of the misplaced Zinc or Copper ions is believed to be very small. Here we use extensive variational optimization to show that the well known $U(1)$-Dirac spin liquid state is extremely sensitive to the introduction of the nonmagnetic Zinc impurity in the Kagome plane. More specifically, we find that the Zinc impurities can significantly reorganize the local spin correlation pattern around them and induce strong spatial oscillation in the magnetic response of the system. We argue that this is a general trend in highly frustrated quantum magnet systems, in which the nonmagnetic impurity may act as strongly relevant perturbation on the emergent resonating valence bond structure in their spin liquid ground state. We also argue that the strong spatial oscillation in the magnetic response should be attributed to the free moment released by the doped Zinc ions and may serve as the smoking gun evidence for the Dirac node in the $U(1)$ Dirac spin liquid state on the Kagome lattice.

Pair Production in time-dependent Electric field at Finite times. (arXiv:2309.12079v2 [hep-ph] UPDATED)
Deepak Sah, Manoranjan P. Singh

We investigate the finite-time behavior of pair production from the vacuum by a time-dependent Sauter pulsed electric field using the spinor quantum electrodynamics (QED). In the adiabatic basis, the one-particle distribution function in momentum space is determined by utilizing the exact analytical solution of the Dirac equation. By examining the temporal behavior of the one-particle distribution function and the momentum spectrum of created pairs in the sub-critical field limit $(E_0 = 0.2E_c)$, we observe oscillatory patterns in the longitudinal momentum spectrum(LMS) of particles at finite times. These oscillations arise due to quantum interference effects resulting from the dynamical tunneling. Furthermore, we derive an approximate and simplified analytical expression for the distribution function at finite times, which allows us to explain the origin and behavior of these oscillations. Additionally, we discuss the role of the vacuum polarization function and its counter term to the oscillations in LMS vacuum excitation. We also analyse the transverse momentum spectrum (TMS).

Homotopy, Symmetry, and Non-Hermitian Band Topology. (arXiv:2309.14416v2 [cond-mat.mes-hall] UPDATED)
Kang Yang, Zhi Li, J. Lukas K. König, Lukas Rødland, Marcus Stålhammar, Emil J. Bergholtz

Non-Hermitian matrices are ubiquitous in the description of nature ranging from classical dissipative systems, including optical, electrical, and mechanical metamaterials, to scattering of waves and open quantum many-body systems. Seminal K-theory classifications of non-Hermitian systems based on line and point gaps have deepened the understanding of many physical phenomena. However, ample systems remain beyond this description; reference points and lines are in general unable to distinguish whether multiple non-Hermitian bands exhibit band crossings and braids. To remedy this we consider the complementary notions of non-Hermitian band gaps and separation gaps that crucially include a broad class of multi-band scenarios, enabling the description of generic band structures with symmetries. With these concepts, we provide a unified and systematic classification of both gapped and nodal systems in the presence of physically relevant parity-time ($\mathcal{PT}$) and pseudo-Hermitian symmetries using homotopy theory. This uncovers new fragile phases and, remarkably, also implies new stable phenomena stemming from the topology of both eigenvalues and eigenvectors. In particular, we reveal different Abelian and non-Abelian phases in $\mathcal{PT}$-symmetric systems, described by frame and braid topology. The corresponding invariants are robust to symmetry-preserving perturbations that do not close band gaps, and they also predict the deformation rules of nodal phases. We further demonstrate that spontaneous $\mathcal{PT}$ symmetry breaking is captured by a Chern-Euler description, a fingerprint of unprecedented non-Hermitian topology. These results open the door for theoretical and experimental exploration of a rich variety of novel topological phenomena in a wide range of physical platforms.

Found 5 papers in prb
Date of feed: Thu, 12 Oct 2023 03:17:06 GMT

Search terms: (topolog[a-z]+)|(graphit[a-z]+)|(rhombohedr[a-z]+)|(graphe[a-z]+)|(chalcog[a-z]+)|(landau)|(weyl)|(dirac)|(STM)|(scan[a-z]+ tunne[a-z]+ micr[a-z]+)|(scan[a-z]+ tunne[a-z]+ spectr[a-z]+)|(scan[a-z]+ prob[a-z]+ micr[a-z]+)|(MoS.+\d+|MoS\d+)|(MoSe.+\d+|MoSe\d+)|(MoTe.+\d+|MoTe\d+)|(WS.+\d+|WS\d+)|(WSe.+\d+|WSe\d+)|(WTe.+\d+|WTe\d+)|(Bi\d+Rh\d+I\d+|Bi.+\d+.+Rh.+\d+.+I.+\d+.+)|(BiTeI)|(BiTeBr)|(BiTeCl)|(ZrTe5|ZrTe.+5)|(Pt2HgSe3|Pt.+2HgSe.+3)|(jacuting[a-z]+)|(flatband)|(flat.{1}band)|(LK.{1}99)

General analytical algorithm of mechanical properties for $1H\text{−}M{X}_{2}$ transition metal dioxides and dichalcogenides
Dong Li, Junfei Zhao, Yonggang Zheng, Hongwu Zhang, and Hongfei Ye
Author(s): Dong Li, Junfei Zhao, Yonggang Zheng, Hongwu Zhang, and Hongfei Ye

2D transition-metal dioxides and dichalcogenides with $1H$ phase ($1H\text{−}M{X}_{2}$) have a large number of members and a wide range of material properties, making them promising candidates for numerous applications. The comprehensive, accurate, and rapid evaluation on the mechanical properties o…

[Phys. Rev. B 108, 144103] Published Wed Oct 11, 2023

Type-II Dirac points and Dirac nodal loops on the magnons of a square-hexagon-octagon lattice
Meng-Han Zhang and Dao-Xin Yao
Author(s): Meng-Han Zhang and Dao-Xin Yao

We study topological magnons on an anisotropic square-hexagon-octagon lattice which has been found by a two-dimensional biphenylene network. We propose the concept of type-II Dirac magnonic states where new schemes to achieve topological magnons are unfolded without requiring the Dzyaloshinskii-Mori…

[Phys. Rev. B 108, 144407] Published Wed Oct 11, 2023

Non-Hermitian parent Hamiltonian from a generalized quantum covariance matrix
Yin Tang and W. Zhu
Author(s): Yin Tang and W. Zhu

Quantum inverse problem is defined as how to determine a local Hamiltonian from a single eigenstate. This question is valid not only in Hermitian system but also in non-Hermitian system. So far, most attempts are limited to Hermitian systems, while the possible non-Hermitian solution remains outstan…

[Phys. Rev. B 108, 165114] Published Wed Oct 11, 2023

Coupling between the spatially separated magnetism and the topological band revealed by magnetotransport measurements on ${\mathrm{EuMn}}_{1−x}{\mathrm{Zn}}_{x}{\mathrm{Sb}}_{2}$ $(0≤x≤1)$
Yuanying Xia, Lin Wang, Yuanhao Zhu, Liyu Zhang, Yan Liu, Xueliang Wu, Long Zhang, Tianran Yang, Kunya Yang, Mingquan He, Yisheng Chai, Huixia Fu, Xiaoyuan Zhou, and Aifeng Wang
Author(s): Yuanying Xia, Lin Wang, Yuanhao Zhu, Liyu Zhang, Yan Liu, Xueliang Wu, Long Zhang, Tianran Yang, Kunya Yang, Mingquan He, Yisheng Chai, Huixia Fu, Xiaoyuan Zhou, and Aifeng Wang

We study the coupling between topological bands and two distinct magnetic sublattices in ${\mathrm{EuMn}}_{1−x}{\mathrm{Zn}}_{x}{\mathrm{Sb}}_{2}$ $(0≤x≤1)$ using a combination of magnetotransport measurements and density functional theory (DFT) calculations. Hall measurements reveal a low carrier c…

[Phys. Rev. B 108, 165115] Published Wed Oct 11, 2023

Long-range correlation-induced effects at high-order harmonic generation on graphene quantum dots
H. K. Avetissian, A. G. Ghazaryan, Kh. V. Sedrakian, and G. F. Mkrtchian
Author(s): H. K. Avetissian, A. G. Ghazaryan, Kh. V. Sedrakian, and G. F. Mkrtchian

This paper focuses on investigating high-order harmonic generation (HHG) in graphene quantum dots (GQDs) under intense near-infrared laser fields. To model the GQD and its interaction with the laser field, we utilize a mean-field approach. Our analysis of the HHG power spectrum reveals fine structur…

[Phys. Rev. B 108, 165410] Published Wed Oct 11, 2023

Found 4 papers in prl
Date of feed: Thu, 12 Oct 2023 03:17:04 GMT

Search terms: (topolog[a-z]+)|(graphit[a-z]+)|(rhombohedr[a-z]+)|(graphe[a-z]+)|(chalcog[a-z]+)|(landau)|(weyl)|(dirac)|(STM)|(scan[a-z]+ tunne[a-z]+ micr[a-z]+)|(scan[a-z]+ tunne[a-z]+ spectr[a-z]+)|(scan[a-z]+ prob[a-z]+ micr[a-z]+)|(MoS.+\d+|MoS\d+)|(MoSe.+\d+|MoSe\d+)|(MoTe.+\d+|MoTe\d+)|(WS.+\d+|WS\d+)|(WSe.+\d+|WSe\d+)|(WTe.+\d+|WTe\d+)|(Bi\d+Rh\d+I\d+|Bi.+\d+.+Rh.+\d+.+I.+\d+.+)|(BiTeI)|(BiTeBr)|(BiTeCl)|(ZrTe5|ZrTe.+5)|(Pt2HgSe3|Pt.+2HgSe.+3)|(jacuting[a-z]+)|(flatband)|(flat.{1}band)|(LK.{1}99)

Optimal Generators for Quantum Sensing
Jarrod T. Reilly, John Drew Wilson, Simon B. Jäger, Christopher Wilson, and Murray J. Holland
Author(s): Jarrod T. Reilly, John Drew Wilson, Simon B. Jäger, Christopher Wilson, and Murray J. Holland

A new method identifies the most sensitive measurement that can be performed using a given quantum state, knowledge key for designing improved quantum sensors.

[Phys. Rev. Lett. 131, 150802] Published Wed Oct 11, 2023

Magneto-Optical Detection of the Orbital Hall Effect in Chromium
Igor Lyalin, Sanaz Alikhah, Marco Berritta, Peter M. Oppeneer, and Roland K. Kawakami
Author(s): Igor Lyalin, Sanaz Alikhah, Marco Berritta, Peter M. Oppeneer, and Roland K. Kawakami

Two different experiments on two different transition metals reveal that a current of electron orbital angular momentum flows in response to an electric field.

[Phys. Rev. Lett. 131, 156702] Published Wed Oct 11, 2023

Orbital Hanle Magnetoresistance in a $3d$ Transition Metal
Giacomo Sala, Hanchen Wang, William Legrand, and Pietro Gambardella
Author(s): Giacomo Sala, Hanchen Wang, William Legrand, and Pietro Gambardella

Two different experiments on two different transition metals reveal that a current of electron orbital angular momentum flows in response to an electric field.

[Phys. Rev. Lett. 131, 156703] Published Wed Oct 11, 2023

Quantum Optics Measurement Scheme for Quantum Geometry and Topological Invariants
Markus Lysne, Michael Schüler, and Philipp Werner
Author(s): Markus Lysne, Michael Schüler, and Philipp Werner

A proposed optical setup combines a Fabry-Perot-type optical cavity with heterodyne photon detection for extracting the topological properties of two-dimensional semiconductor materials.

[Phys. Rev. Lett. 131, 156901] Published Wed Oct 11, 2023

Found 2 papers in pr_res
Date of feed: Thu, 12 Oct 2023 03:17:06 GMT

Search terms: (topolog[a-z]+)|(graphit[a-z]+)|(rhombohedr[a-z]+)|(graphe[a-z]+)|(chalcog[a-z]+)|(landau)|(weyl)|(dirac)|(STM)|(scan[a-z]+ tunne[a-z]+ micr[a-z]+)|(scan[a-z]+ tunne[a-z]+ spectr[a-z]+)|(scan[a-z]+ prob[a-z]+ micr[a-z]+)|(MoS.+\d+|MoS\d+)|(MoSe.+\d+|MoSe\d+)|(MoTe.+\d+|MoTe\d+)|(WS.+\d+|WS\d+)|(WSe.+\d+|WSe\d+)|(WTe.+\d+|WTe\d+)|(Bi\d+Rh\d+I\d+|Bi.+\d+.+Rh.+\d+.+I.+\d+.+)|(BiTeI)|(BiTeBr)|(BiTeCl)|(ZrTe5|ZrTe.+5)|(Pt2HgSe3|Pt.+2HgSe.+3)|(jacuting[a-z]+)|(flatband)|(flat.{1}band)|(LK.{1}99)

Experimental observation of non-Hermitian higher-order skin interface states in topological electric circuits
Bin Liu, Yang Li, Bin Yang, Xiaopeng Shen, Yuting Yang, Zhi Hong Hang, and Motohiko Ezawa
Author(s): Bin Liu, Yang Li, Bin Yang, Xiaopeng Shen, Yuting Yang, Zhi Hong Hang, and Motohiko Ezawa

The study of topological states has developed rapidly in electric circuits, which permits flexible fabrications of non-Hermitian systems by introducing non-Hermitian terms. Here, nonreciprocal coupling terms are realized by utilizing a voltage follower module in non-Hermitian topological electric ci…

[Phys. Rev. Research 5, 043034] Published Wed Oct 11, 2023

Braid-protected topological band structures with unpaired exceptional points
J. Lukas K. König, Kang Yang, Jan Carl Budich, and Emil J. Bergholtz
Author(s): J. Lukas K. König, Kang Yang, Jan Carl Budich, and Emil J. Bergholtz

A class of systems is presented in which a particle-antiparticle pair cannot annihilate each other after they have moved along a loop and instead form a new type of composite particle. This occurs in so-called non-Hermitian systems: classical metamaterials or “open” quantum systems that are coupled to the rest of the Universe. In two dimensions, their excitations are massless “particles” that can be created as a pair or annihilate each other pairwise. Each particle is associated with the mathematical structure of a knot in a rope. After moving one particle along a loop and bringing it near its former antiparticle, their knots are combined differently. The two can no longer annihilate pairwise and instead form a new particle corresponding to a more complicated knot. This shows that non-Hermitian particles in two dimensions remember their movement history.

[Phys. Rev. Research 5, L042010] Published Wed Oct 11, 2023